1. Field of the Invention
The present invention relates to a process for the disproportionation of silanes containing at least one Si--H bond and, more particularly, to an advantageous process for the disproportionation of trichlorosilane to obtain dichlorosilane and ultimately, where desired, silane.
2. Description of the Prior Art
It is of course well known that silane is a preferred starting material for the formation through decomposition of very pure silicon which is particularly valuable for the fabrication of semiconductor devices and/or photovoltaic devices (e.g., solar cells). It is also known that it is possible to obtain silane by the disproportionation of trichlorosilane in the presence of various catalysts according to the following reactions: EQU 2HSiCl.sub.3 .revreaction.H.sub.2 SiCl.sub.2 +SiCl.sub.4 ( 1) EQU 2H.sub.2 SiCl.sub.2 .revreaction.H.sub.3 SiCl+HSiCl.sub.3 ( 2) EQU 2H.sub.3 SiCl.revreaction.SiH.sub.4 +H.sub.2 SiCl.sub.2 ( 3)
Various catalysts for carrying out the above disproportionation reactions have been described in the literature. Thus, for example, French Pat. No. 2,096,605 proposes the use of tertiary amines; French Pat. Nos. 2,118,725 and 2,261,977 suggest the use of anion exchange resins to which tertiary amines or quaternary ammonium groups are bonded; French Pat. No. 2,290,447 describes the use of N-substituted pyrrolidones and French Pat. No. 2,290,448 describes the use of tetraalkylureas.
To obtain acceptable yields, the catalysts which have been heretofore recommended are required to be utilized in relatively large amounts or require that the disproportionation reaction be carried out at elevated temperatures.